1. Field of the Invention
The present invention relates to a dustproof device of a light path system disposed in a laser beam machine and the like.
2. Description of the Related Art
A laser beam machine includes a laser beam path system for supplying laser beam output from a fixed laser oscillator to a machining head moving at high speed.
The laser beam machine for realizing the present invention is equipped with a bed for housing pallets on which workpieces are placed, a column guided via guide rails disposed on both sides of the bed and moving at high speed along the longitudinal direction of the head, and a machining head moving at high speed on guide rails disposed on the column in the direction orthogonal to the direction of movement of the column.
The laser beam path system disposed on the laser beam machine comprises a light path duct disposed along the longitudinal direction of the bed, and a laser beam extraction unit that moves in synchronization with the column for extracting the laser beam passing through the light path duct and sending the same toward the column.
The light path duct is a member having a U-shaped cross-section with the upper portion opened, and in the interior thereof is irradiated a laser beam. A dustproof device is adopted, in which the upper surface of the light path duct is covered by a steel belt, and the steel belt is elevated via a guide roller only where the laser beam extraction unit passes, so as to enable the laser beam to be extracted.
Japanese patent application No. 2004-118483 discloses a dustproof unit of a laser beam machine filed by the present applicant.
In the dustproof unit of a laser beam machine disclosed in the above-mentioned patent application, a belt-like magnet is disposed on both sides of the light path duct, attracting the steel belt and preventing foreign substances from entering the duct.
However, there is a drawback in that when the laser beam extraction unit passes, the steel belt is forcibly elevated by the guide roller, and when it is lowered onto the magnet after the passing of the extraction unit, the belt is displaced and not returned to its original position.
This displacement of the return position of the steel belt accompanying the raising and lowering of the steel belt causes dust to be generated by friction with the guide roller, which causes deterioration of the dustproof operation and also causes damage to the steel belt when the laser beam extraction unit passes at high speed.